"I have sent a legal notice (to Sisodia) as regularising contract teachers without giving an opportunity to others for such appointments is wrong," Bhushan said.

"The Supreme Court had said such appointments would be illegal as other outsiders too deserve an equal chance. Some of the disgruntled teachers had come to me and on their behalf I have sent the notice and sought a reply within seven days," said Bhushan, who was expelled from the Aam Aadmi Party in April for alleged anti-party activities.

As per the notice sent to Sisodia, who also holds the education portfolio, the directorate of education's circular for regularising of existing guest/contract teachers would result in "denial of fair opportunity" to other candidates who are otherwise qualified and eligible, but did not work earlier as guest teacher.

Bhushan's notice said: "It is appropriate for the state government to employ regular, full-time teachers instead of guest teachers, but everyone has to get an opportunity to compete for employment opportunities with state."

“By this notice, you are hereby required to immediately enlarge the scope of candidates for the exam and permit all eligible candidates. In case you fail to comply, and no action is taken within seven days, my clients have no option but to approach the court," it said.